PURPOSE: Drug-resistant supraventricular tachycardia can cause hemodynamic instability, especially in infants. There are no case-series reports of transcatheter cryoablation treatment for infants with drug-resistant supraventricular tachycardia. Our purpose is to report our experience with transcatheter cryoablation in three infants with drug-resistant supraventricular tachycardia.METHODS: We reviewed clinical and electrophysiologic data from infants who underwent cryothermal ablation for drug-resistant supraventricular tachycardia (SVT) at our institution.RESULTS: Three patients (age 10-42 days) underwent transcatheter cryothermal ablation over a 1-year period. None had arrhythmia suppression on medical management, and all had hemodynamic instability from persistent SVT episodes. Cryothermal mapping (-30 C) localized the suspected foci. All foci were adjacent to the AV node. Cryoablation lesions were delivered at and around mapped foci. In one patient, cryothermal energy application eliminated the SVT but resulted in transient right bundle branch block that resolved later. Two patients had hemodynamically insignificant episodes of SVT in the immediate post-ablation period that resolved with standard antiarrhythmic treatment. One died of sepsis but remained SVT free for 10 days after the procedure without antiarrhythmic medications. Neither of the two surviving patients had SVT recurrence at 6-month follow-up off medications.CONCLUSIONS: In our series, transcatheter cryoablation was an effective treatment for drug-resistant SVT in infants. We encountered some early nonsustained post-procedure SVT; however, such episodes did not predict procedural failure.